1. Field of the Invention
The invention relates in general to a projection device and a control method thereof, and more particularly to a projection device which changes the way of controlling the MEMS module and a control method thereof.
2. Description of the Related Art
The micro projection device normally uses a micro electro mechanical system (MEMS) module to reflect a light beam generated by a light source such that the light beam is projected on a projection surface for generating desired images. In general, the reflection angle of the reflection surface of the MEMS module is controlled by an x-direction (the horizontal direction) control signal and a y-direction (the vertical direction) control signal, such that the light beam can scan along the horizontal direction and the vertical direction to form desired images.
In terms of the y-direction scanning, different control voltages will result in different reflection angles of the reflection surface of the MEMS module, and the projection angle of the light beam along the y direction is determined according to the reflection angles of the reflection surface. In order to increase the projection range along the y direction, the magnitude of the control voltage needs to be increased. However, the control voltage inputted to the MEMS module has a predetermined upper limit, and if the inputted control voltage is over the predetermined upper limit, it may lead to pull-in effect or damage in MEMS module.
Therefore, how to provide a control method of a projection device capable of increasing the projection range along the y direction and at the same time avoiding the MEMS pull-in effect or MEMS module damage has become a prominent task for the industries.